For an LTE (Long Term Evolution) multicarrier system, to support a wider system bandwidth than the system, for example, 100 MHz, one possible way is to directly allocate the spectrum of 100M bandwidth as shown in FIG. 1; another possible way is to aggregate some spectra allocated to the existing system to constitute a large bandwidth for the system. At this time, uplink and downlink carriers in the system can be configured asymmetrically, that is to say, users may occupy N (N≧1) carriers for downlink transmission and M (M≧1) carriers for uplink transmission as shown in FIG. 2.
An LTE-A (Long Term Evolution Advanced) system can support 5 carriers at most now for aggregation. An LTE-A UE (User Equipment) should feedback the ACK (Acknowledgement)/NACK (Negative Acknowledgement) feedback information of several downlink carriers and sub-frames in one uplink sub-frame. At present, in the LTE-A system, the number of ACK/NACK information bits fed back by UE is determined based on the configured downlink carriers and the transmission mode of each downlink carrier, that is to say, in a FDD (Frequency Division Duplex) system, UE should feed back
      ∑          i      =      1        N    ⁢          ⁢      C    i  bits of ACK/NACK in an uplink sub-frame, wherein, Ci refers to the number of codewords of each downlink carrier (C=1 during single-codeword transmission, while C=2 during multiple-codeword transmission), the transmission mode (namely the number of codewords) of different downlink carriers can be different and N means the number of downlink carriers configured by UE. In a TDD (Time Division Duplex) system, UE should feed back
      ∑    i    N    ⁢          ⁢            C      i        ·          M      i      bits of ACK/NACK in an uplink sub-frame, wherein, Mi is the number of downlink sub-frames for UE to feed back the ACK/NACK in an uplink sub-frame of the ith carrier and M, namely the number of K in each column of Table 1, is different for different downlink configurations and uplink sub-frames, which corresponds to several downlink sub-frames for the same uplink sub-frame to feed back the ACK/NACK, hereinafter referred to as “feedback window”.
TABLE 1Downlink Association Set Index K: {k0, k1, ...kM−1} for TDDUL-DLSubframe nConfiguration01234567890——6—4——6—41——7, 64———7, 64—2——8, 7, 4, 6————8, 7——4, 63——7, 6, 116, 55, 4—————4——12, 8, 7, 116,5,——————4, 75——13, 12, 9, 8, 7, 5,———————4, 11, 66——775——77—
In an LTE-A system, PUCCH (Physical Uplink Control Channel) format 1b with to channel selection and PUCCH format 3 can be adopted as the multiplexing transmission scheme for not more than 4 bits of ACK/NACK information, wherein, the maximum number of transmission bits for the PUCCH format 1b with channel selection transmission scheme is 4 bits. PUCCH format 3 is a new ACK/NACK transmission scheme based on DFT-S-OFDM with the structure shown in FIG. 3, wherein, RM (32,O) block codes are used for channel encoding to transmit 20 bits of the feedback information at most. Spread spectrum sequences with the spreading factor of 5 are adopted in a time domain, so a PRB (Physical Resource block) can multiplex 5 users for simultaneous transmission. PUCCH format 2/2a/2b or PUCCH format 3 can be adopted as the transmission scheme of the periodic CQI (Channel Quality Indication)/PMI (Precoding Matrix Indicator)/RI (Rank Indication) information.
Meanwhile, such information can be transmitted on channel resources configured at a higher layer according to the defined period.
In an LTE-A system, time domains or frequency domains can be bundled to decrease the number of ACK/NACK feedback bits.
(1) Time-domain bundling means that UE bundles the ACK/NACK feedback information corresponding to data packets received in several downlink sub-frames of feedback windows in a configured downlink carrier and acquires L bits of bundled ACK/NACK feedback information b0, b1, . . . bL-1 as shown in FIG. 4, wherein, N≧L≧2N, and N is the number of downlink carriers aggregated by UE. If the configured downlink carrier is in multiple-codeword transmission mode, UE should also perform spatial bundling on 2N-L configured downlink carriers, namely bundling the ACK/NACK feedback information of multiple-codeword received in an uplink sub-frame on the carrier. Feedback information states comprise ACK (correctly-received data packets), NACK (incorrectly-received data packets) and DTX (Discontinuous Transmission, indicating missed or unscheduled data packets). During bundling, UE can detect whether downlink data packets of the currently-configured downlink carrier have been missed in a feedback window or whether it receives any data packets on the currently-configured downlink carrier in a feedback window by using the DAI (Downlink Assignment Index), and then generate the DTX for such a downlink carrier as the bundled feedback information. If UE detects that no downlink data packets have been missed on such downlink carrier in the feedback window and the feedback information of at least a data packet received in downlink carrier is NACK, it is necessary to generate the NACK for the downlink carrier as the bundled feedback information. If UE detects that no downlink data packets have been missed on such downlink carrier in the feedback window and the feedback information of all data packets received on the downlink carrier is ACK, it is necessary to generate the ACK for the downlink carrier as the bundled feedback information.
To eliminate an inconsistent understanding of UE and base stations caused by data packet losses when bundling in time domains, UE can take the number of the last downlink sub-frame received in a feedback window or the total number of downlink sub-frames in a feedback window as ┌log2 M┐ bits of assistant information, {tilde over (b)}0, {tilde over (b)}1, . . . {tilde over (b)}┌log2M┐−1 and cascade it with the bundled ACK/NACK feedback information to form L+┌log2 M┐ bits of feedback information for transmission. In this way, a base station can detect whether the finally-scheduled data packets have been missed or whether data packets in a feedback window have been missed by using the ┌log2 M┐ bits of the rear information in the received feedback bits, so as to determine a proper retransmission decision and improve system transmission efficiency.
Frequency-domain bundling means that UE bundles the ACK/NACK information of data packets received on each configured downlink carrier in the current downlink sub-frame in a feedback window and performs spatial bundling if the configured downlink carrier is in multiple-codeword transmission mode. A schematic diagram of bundling frequency domains of the ACK/NACK feedback information in the prior art is shown in FIG. 5. To judge missed data packets, 2 bits of DAI in DL grant (DownLink grant) of an LTE TDD system can be used to indicate the total number of downlink data packets scheduled and transmitted on the configured downlink carriers in the same downlink sub-frame in a feedback window.
During bundling, if UE detects that downlink data packets on the configured downlink carrier in the current downlink sub-frame of the feedback window have been missed or UE does not receive downlink data packets in all the configured downlink carriers of the current downlink sub-frame, it is necessary to generate the DTX for the downlink sub-frame as the bundled feedback information. If UE detects that no downlink data packets have been missed on all the configured downlink carrier in current downlink subframe of the feedback window and the feedback information of at least a data packet received on multiple configured downlink carrier in current downlink subframe is NACK, it is necessary to generate the NACK for current downlink subframe as the bundled feedback information. If UE detects that no downlink data packets have been missed on all the configured downlink carrier in current downlink subframe of the feedback window and the feedback information of all data packets received on multiple configured downlink carrier in current downlink subframe is ACK, it is necessary to generate the ACK for current downlink subframe as the bundled feedback information.
In an LTE Rel-8 system, a base station can configure in a semi-static state whether UE supports the simultaneous transmission of ACK/NACK and periodic CQI/PMI/RI in a PUCCH through the parameter, simultaneousAckNackAndCQI. If the parameter is False, simultaneous transmission is not supported, that is to say, when ACK/NACK and periodic CQI/PMI/RI happened to be transmitted in the same uplink sub-frame through a PUCCH, UE will drop the periodic CQI/PMI/RI and only feed back ACK/NACK. If the parameter is True, simultaneous transmission is supported. At this time, ACK/NACK feedback bits indicate 1 bit of ACK/NACK information of a data packet when only the data packet is available or the number of ACK in the ACK/NACK feedback information of several scheduled data packets when they are available as shown in Table 2. Under the normal CP, PUCCH format 2a/2b is used to transmit periodic CQI/PMI/RI feedback bits and ACK/NACK feedback bits will be mapped in pilot frequency resources in the 2nd column to be transmitted together with the periodic CQI/PMI/RI feedback bits. Under the extended CP, PUCCH format 2 is adopted to transmit periodic CQI/PMI/RI feedback bits and the combined code transmission will be performed on the cascaded ACK/NACK feedback bits after periodic CQI/PMI/RI feedback bits.
TABLE 2Multi-ACK/NACK Feedback Information MappingNumber of ACK among multiple(UDAI + NSPS) ACK/NACK responsesb(0), b(1)0 or None (UE detects at least one0, 0DL assignment is missed)11, 121, 030, 141, 151, 060, 171, 181, 090, 1
In the procedure of realizing the objects of the present invention, at least the following problems existing in the current technologies were found:
In an LTE-A system, there may be a lot of ACK/NACK feedback information bits and 20 bits of information at most can be transmitted using PUCCH format 3, the mode of transmitting ACK/NACK and periodic CQI/PMI/RI simultaneously in an LTE Rel-8 is no longer applicable to the LTE-A system entirely.
At present, there is no solution for transmitting ACK/NACK and periodic CQI/PMI/RI simultaneously in multiple carriers in the prior art.